The furnace hearth of the first-generation blast furnace was seriously eroded. Although corresponding furnace protection measures were taken, the expected results were not achieved. After analyzing the causes of corrosion, the new generation of furnaces began to take the following long-life furnace protection measures:
(1) Strengthen the quality management of raw materials and fuels, strictly control the amount of alkali metal and Zn into the furnace, the Zn load is basically within 15kg/t, strictly control the use of raw materials with high content of alkali metal and Zn, and control the amount of alkali metal into the furnace < 2kg per ton of iron /t, Zn<0.10kg/t.
(2) Optimizing the operating system and stabilizing the heat load of the furnace body
During the production period of the first generation of blast furnace, the antegrade state has not been ideal. The phenomenon of material collapse and slip occurred from time to time, the distribution of air flow was unreasonable, and the furnace temperature fluctuated greatly when the furnace condition was restored. In May 2013, the charging system was gradually optimized, the batch weight of ore was increased, the depth of the material line was appropriately increased, the edge load was reduced, and the edge airflow was released while stabilizing the central airflow. Through the adjustment, the air permeability is improved and the gas flow distribution tends to be reasonable, the heat load of the furnace hearth and the furnace body is stable, the difficult operation situation is obviously improved, and the influence of the wall fluctuation on the furnace condition adjustment is eliminated.
(3) Improved cooling system
Due to the small diameter of the main cooling water pipeline in the first-generation hearth, the water volume of the hearth cannot be increased, resulting in a small water volume in the hearth. A φ600mm pipe is added to the second-generation cooling water ring pipe to increase the water volume of the hearth from 1900m3 to 2700m3.
(4) Welding and repairing the leakage point of the furnace body, increasing the temperature detection of the furnace skin
The leakage point of the furnace body is a major hidden danger and must be properly handled. The blast furnace performs welding repairs on the leaking parts of the furnace skin, and adopts external cooling measures for high temperature areas. Infrared temperature measurement is regularly carried out on key parts of the furnace skin in each shift, and an alarm system is established to ensure that the furnace skin cooling is always in a controllable state.
(5) Strengthen tapping management
In the daily operation, the diameter of the drill bit of the opening machine should be reasonably selected to ensure that the slag and iron can be discharged within a reasonable time range, and try to avoid the situation of simultaneous tapping in two fields. Tapping at intervals of 10 minutes is adopted, the depth of the blast furnace tap hole is controlled at 3±0.2m, the tapping time is controlled at about 100 minutes, and the number of tapping times per day is controlled at about 12 times.
Improved clay quality. The quality of the gun mud has a great influence on the depth of the stable taphole. In the later stage of the furnace operation, the amount of iron passing through the four tapholes is quite different. By rationally adjusting the proportion of blasting mud, different strengths of blasting mud can be used in a targeted manner according to the needs of different tapholes.
Protect the mud jacket. In the production, the completeness of the mud jacket should be ensured, and the inspection should be carried out carefully after each tapping. If any defects are found, a new mud jacket must be made again.
(6) Strengthen the monitoring of water leakage in the cooling system
Water leakage from the damaged cooling wall into the furnace will promote the oxidation of hearth carbon bricks, so water leakage from the cooling system to the furnace should be avoided as much as possible, and once water leakage is found, it should be replaced as soon as possible. Regularly analyze the content of H2 in the furnace top gas composition, monitor the fluctuation of cooling wall replenishment curve in real time, strengthen the inspection of on-site cooling equipment, and comprehensively judge whether the cooling equipment is damaged.
(7) Formulate temperature control standards
The copper stave is controlled at 55±5°C, and the temperature of the ductile iron stave is not allowed to exceed 200°C for a long time, otherwise the temperature of the inner surface of the stave may exceed 400°C, which will cause the performance of the ductile iron to deteriorate, and the strength and elongation will drop rapidly . The temperature of the 6th stage cooling wall is controlled at 50~60℃, and the temperature of the 8th stage cooling wall is controlled at 80~130℃.